Medical device having asymmetric bending

ABSTRACT

An articulation joint includes proximal links, distal links, and intermediate links connecting the proximal and distal links. The articulation joint has a straight configuration along a straight longitudinal axis, a first bent configuration when the articulation joint bends toward a first side of the longitudinal axis, and a second bent configuration when the articulation joint bends toward a second side of the longitudinal axis, opposite to the first side. When the articulation joint is in the straight configuration, a first gap is defined at the first side between adjacent proximal links, and the adjacent proximal links contact each other at the second side, a second gap is defined at each of the first side and the second side between adjacent distal links, and a third gap is defined at the first side between adjacent intermediate links, and adjacent intermediate links contact each other at the second side.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from U.S. ProvisionalApplication No. 62/848,195, filed May 15, 2019, which is incorporated byreference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to endoscopic medical devicesand methods of use. More particularly, in some embodiments, thedisclosure relates to endoscopes and methods related for accessingtarget sites having space constraints, using, e.g., a flexible steerableshaft such as an articulation joint at a distal end of the endoscope.

BACKGROUND

Endoscope devices generally include a flexible shaft, a working distaltip, and a flexible steerable shaft joining the working tip and theflexible shaft. The flexible steerable shaft may include a bendablearticulation joint. Drawbacks of conventional endoscopes include, forexample, the inability to provide a small bend radius when thearticulation joint provides both large and small bend angles. Forexample, articulation joints providing full retroflex (bending of thearticulation joint to visualize proximally, for example an entry portalof the endoscope into a patient's stomach) generally require thearticulation joint to bend by approximately 210 degrees or more. Whenthe same conventional articulation joint is bent to less than 210degrees, e.g., a 90 degree position, the articulation joint will make agradual turn with a large radius, which is not suitable for areas of thehuman body having space constraints. These drawbacks can prevent thephysician from properly visualizing and/or accessing areas of the bodyduring procedures.

Accordingly, it is desirable for the articulation joint to provide atightest acceptable bend radius when flexing the articulation joint to amaximum angle, and to achieve the same or similar tightest acceptablebend radius when flexing the articulation joint to a smaller angle. Thepresent disclosure may solve one or more of these problems or otherproblems in the art. The scope of the disclosure, however, is defined bythe attached claims and not the ability to solve a specific problem.

SUMMARY OF THE DISCLOSURE

According to an example, an articulation joint for a medical deviceincludes proximal links, distal links, and intermediate links connectingthe proximal and distal links. The articulation joint has a straightconfiguration along a straight longitudinal axis, a first bentconfiguration when the articulation joint bends toward a first side ofthe longitudinal axis, and a second bent configuration when thearticulation joint bends toward a second side of the longitudinal axis,opposite to the first side. When the articulation joint is in thestraight configuration, a first gap is defined at the first side betweenadjacent proximal links, and the adjacent proximal links contact eachother at the second side, a second gap is defined at each of the firstside and the second side between adjacent distal links, and a third gapis defined at the first side between adjacent intermediate links, andadjacent intermediate links contact each other at the second side.

When the articulation joint is in the first bent configuration, a sizeof each of the first, second, and third gaps on the first side, may besmaller than a size of the first, second, and third gaps on the firstside respectively when the articulation joint is in the straightconfiguration.

When the articulation joint is completely bent toward the first side,surfaces of adjacent links may contact each other such that the side ofeach of the first, second, and third gaps on the first side is zero.

When the articulation joint is in the second bent configuration, a sizeof the second gaps on the second side may be smaller than a size of thesecond gaps on the second side when the articulation joint is in thestraight configuration.

The distal links may be movable in exactly four directions, the proximallinks may be movable in exactly one direction, and the intermediatelinks may be movable in two or three directions.

The articulation joint may include a third bent configuration toward athird side of the longitudinal axis, intermediate to the first andsecond sides, and a fourth bent configuration when the articulationjoint bends toward a fourth side of the longitudinal axis, opposite tothe third side, such that when the articulation joint is in the straightconfiguration, a fourth gap may be defined at each of the third side andthe fourth side between the adjacent distal links, and a fifth gap maybe defined at each of the third side and the fourth side between theadjacent intermediate links.

When the articulation joint is in the third bent configuration, a sizeof each of the fourth gaps and the fifth gaps on the third side may besmaller than a size of the fourth gaps and the fifth gaps on the thirdside respectively when the articulation joint is in the straightconfiguration, and when the articulation joint is in the fourth bentconfiguration, a size of each of the fourth gaps and the fifth gaps onthe fourth side may be smaller than a size of the fourth gaps and thefifth gaps on the fourth side respectively when the articulation jointis in the straight configuration.

The fourth gaps and the fifth gaps may be offset from the first, second,and third gaps along the longitudinal axis.

The articulation joint may move in one of the first or the seconddirection and one of the third or the fourth direction at a same time.

Proximal links, distal links, and intermediate links of the articulationjoint may be each attached to an adjacent link by a first spring and asecond spring, and the first spring and the second spring of attachedlinks may be on circumferentially opposite sides of the articulationjoint.

The first and the second springs may be attached on an inner surface ofeach of the proximal links, distal links, and intermediate links by oneor more of welding, brazing, soldering, or an adhesive.

Adjacent coils of each of the first spring and the second spring maycontact each other when the first springs and the second springs are ina straight configuration.

Each of the first spring and the second spring may define a lumen forcontaining an articulation element.

A bend angle associated with each of the first, second, third, fourth,and fifth gaps may be equal.

The articulation joint may include a tip portion attached to a distalend of the distal links, wherein the tip portion includes one or more ofan imaging device, lighting device, an end effector, and a cannulationfor passage of secondary instrumentation.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate various exemplary embodiments andtogether with the description, serve to explain the principles of thedisclosed embodiments.

FIG. 1 is a perspective view of a medical device according to anembodiment;

FIG. 2 is a cross-section of an articulation joint of the medical deviceaccording to FIG. 3 along the line A-A;

FIG. 3 is a perspective view of the articulation joint of FIG. 2 ; and

FIGS. 4A-4F are side views of the articulation joint of FIG. 3 .

DETAILED DESCRIPTION

Both the foregoing general description and the following detaileddescription are exemplary and explanatory only and are not restrictiveof the features, as claimed. As used herein, the terms “comprises,”“comprising,” “having,” “including,” or other variations thereof, areintended to cover a non-exclusive inclusion such that a process, method,article, or apparatus that comprises a list of elements does not includeonly those elements, but may include other elements not expressly listedor inherent to such a process, method, article, or apparatus. In thisdisclosure, relative terms, such as, for example, “about,”“substantially,” “generally,” and “approximately” are used to indicate apossible variation of ±10% in a stated value or characteristic.

Referring to FIG. 1 , an endoscope 10 according to an embodiment isshown. Endoscope 10 includes a flexible shaft 20, a tip 30 at a distalend of endoscope 10, and an articulation joint 50 disposed between andconnecting flexible shaft 20 and tip 30. A handle 40 or some otherdevice for actuating or controlling endoscope 10, and any tool ordevices associated with endoscope 10, is connected at a proximal end offlexible shaft 20.

A plurality of actuating elements 12, such as cables or wires suitablefor medical procedures (e.g., medical grade plastic or metal), extenddistally from a proximal end of endoscope 10. Actuating elements 12 areshown between adjacent links in, e.g., FIGS. 4A-4F. Actuating elements12 may extend into handle 40 and may be indirectly coupled to first andsecond actuating devices 42, 43, which control articulation ofarticulation joint 50 in multiple directions. Devices 42, 43, may be,for example, rotatable knobs that rotate about their axes to push/pullactuating elements 12. Alternatively, or additionally, a user mayoperate actuating elements 12 independently of handle 40. Distal ends ofactuating elements 12 extend through flexible shaft 20 and terminate atactuating joint 50 and/or tip 30. For example, one or more actuatingelements 12 may be connected to articulation joint 50 and one or moreother actuating elements 12 may be attached to tip 30. As will beexplained herein, actuation of actuating elements 12 may controlactuating joint 50, tip 30, and/or elements attached to tip 30, such asan end effector (not shown). In addition, one or more electrical cables(not shown) may extend from the proximal end of endoscope 10 to tip 30and may provide electrical controls to imaging, lighting, and/or otherelectrical devices on tip 30, and may carry imaging signals from tip 30proximally to be processed and/or displayed on a display. Handle 40 mayalso include ports 44, 46 for introducing and/or removing tools, fluids,or other materials from the patient. Port 44 may be used to introducetools. Port 46 may be connected to an umbilicus for introducing fluidsuction, and/or wiring for electronic components.

As shown in FIG. 2 , articulation joint 50 includes a portion of a lumen22 that extends through endoscope 10. Articulation joint 50 alsoincludes a plurality of springs 24. For ease of understanding, only someof the plurality of springs 24 are identified in FIG. 3 . Further,springs 24 have been removed in FIGS. 4A-4F for ease of understanding(springs 24 are located between pairs of laser welds 28, describedbelow). Springs 24 connect adjacent links of articulation joint 50, aswill be described in greater detail herein. Lumen 22 may extend fromhandle 40 through flexible shaft 20 into articulation joint 50, andthrough a distal end of tip 30. Lumen 22 may receive tools, imagingdevices, and other devices associated with endoscope 10 to performendoscopic procedures. Further, tissue samples and/or other material maybe removed from a patient through lumen 22. It will be understood thatendoscope 10, including flexible shaft 20 and articulation joint 50, arenot limited to a single lumen 22, and may include any number of lumensnecessary for performing procedures. Alternatively, or additionally, oneor more catheters (not show) may be introduced through lumen 22 toremove tissue and/or insert tools.

With continued reference to FIG. 2 , springs 24 define actuation holes25 which receive actuation elements 12. According to an example, oneactuating element or a plurality of actuating elements 12 may bedisposed in a single actuation hole 25 of each spring 24. Additionalactuation holes, such as eyelets (not shown), may extend from a proximalend of flexible shaft 20 to a distal end thereof, and may provide a paththrough which actuation elements 12 may extend, thereby preventingactuating elements 12 from becoming tangled or otherwise adverselyaffecting an operation of endoscope 10.

With reference to FIG. 3 , a distalmost link 29 may connect to tip 30.Tip 30 may include a camera (not shown), lighting, electronics (such asa printed circuit board), an end effector or tool (not shown), or anyother device used in a therapeutic or a diagnostic procedure. It will beunderstood that tip 30 may include multiple elements, e.g., both thecamera and the end effector, to both visualize a target site and tocollect samples from the target site.

Articulation joint 50 will be described with reference to FIGS. 3 and4A-4F. Articulation joint 50 includes a plurality of generallycylindrical links with a plurality of gaps provided therebetween. Forexample, as shown in FIG. 3 , articulation joint 50 includes a firstproximal link section 52, a third distal link section 56, and a secondintermediate link section 54 provided between and connecting the firstlink section 52 and the third link section 56. First, second, and thirdlink sections 52, 54, 56 are formed of a first link type 50 a, a secondlink type 50 b, and a third link type 50 c, respectively (see FIG. 4C).According to an example, first, second, and third link types 50 a, 50 b,50 c may be the same or different shapes and/or sizes. For example,first link type 50 a is longer along longitudinal axis A than second andthird link types 50 b, 50 c. Unless specified otherwise, first link type50 a, second link type 50 b, and third link type 50 c will generally bereferred to as a “link.” Links may be formed by, for example, lasercutting a tube (such as a metal tube, a plastic tube, or any othermedical grade material known in the art), but are not limited to beingformed in this manner.

As further shown in FIGS. 2 and 3 , springs 24 join adjacent links ineach of first, second, and third link sections 52, 54, 56. Additionally,springs 24 may connect a distalmost link of first link section 52 to aproximalmost link of second link section 54, may connect a distalmostlink of second link section 54 to a proximalmost link of third linksection 56, and/or may connect a distalmost link of third link section56 to distalmost link 29. As will be described in greater detail herein,adjacent links are capable of bending with respect to each other due tospacing between links and via the flexibility of springs 24. Whileexamples illustrate two springs 24 joining adjacent links, the inventionis not limited to this configuration. According to an example, springs24 are attached to an inner surface of articulation joint 50 by, e.g.,laser welding, adhesives, rivets, or any other technique known in theart. For example, laser welds 28 are shown on adjacent links in FIG. 3at locations at which springs 24 are attached.

As shown in FIGS. 4B and 4E, articulation joint 50 is in a straightconfiguration and includes a longitudinal axis A extending through acenter of each of first, second, and third link sections 52, 54, 56.Articulation joint 50 is configured to bend in four different directions90 degrees apart from each other about axis A (e.g., up, down, left andright directions). The directions of bending are designated as firstside 58 a, second side 58 b, third side 58 c, and fourth side 58 d,approximately 90 degrees from each adjacent side. First side 58 a isopposite second side 58 b (approximately 180 degrees apart), and thirdside 58 c is opposite fourth side 58 d (approximately 180 degreesapart). As shown in FIGS. 4A, 4C, 4D, and 4F, links are bent in each offirst, second, and/or third link sections 52, 54, 56 with respect toeach other. As further shown in FIGS. 4A-4F, springs 24 are located ononly two adjacent sides, e.g., third side 58 c and fourth side 58 d, offirst link section 52. As will be described in greater detail below,springs 24 are located on first, second, third, and fourth sides 58 a,58 b, 58 c, 58 d of second link section 54 and third link section 56.

As shown in FIGS. 4C and 4F, each link includes an end surface 51 facingan adjacent link and, in some instances, end surfaces 51 of adjacentlinks are in contact when articulation joint 50 is in the straightconfiguration. For example, end surface 51 of first link 50 a contactsan end surface 51 of an adjacent link 50 a on one of four sides ofarticulation joint 50 (e.g., second side 58 b) when articulation joint50 is in the straight configuration (contact may include point contactbetween adjacent end surfaces 51 at second side 58 b of adjacent links50 a, and/or contact between adjacent surfaces 51 of adjacent links 50 afrom second side 58 b toward one or both of first and third sides 58 a,58 c in a circumferential direction of articulation joint 50). For easeof understanding, only some end surfaces 51 are identified by areference numeral in FIGS. 4A-4F. However, it will be understood thatend surfaces 51 are provided at each end of every link.

On first side 58 a of first link section 52, end surface 51 of one link50 a is spaced from end surface 51 of an adjacent link 50 a, approachesend surface 51 of the adjacent link 50 a as articulation joint 50 bendstoward first side 58 a, and contacts end surface 51 of the adjacent link50 a when articulation joint 50 is completely bent toward first side 58a, as shown in FIG. 4A. As described above, springs 24 connect adjacentlinks 50 a on only two sides, e.g., third side 58 c and fourth side 58d. In addition, springs 24 are tightly wound coiled springs with nospaces between adjacent coils when the spring is in a straightconfiguration. For this reason, links having a first link type 50 a infirst link section 52 are incapable of bending toward third side 58 c orfourth side 58 d. According to an embodiment, therefore links 50 a offirst link section 52 bend in a single direction, e.g., toward firstside 58 a.

As further shown in FIGS. 4B and 4E, end surface 51 of a second link 50b contacts end surface 51 of an adjacent link 50 b on only one side,i.e., second side 58 b, when articulation joint 50 is in the straightconfiguration. End surface 51 of third link type 50 c does not contactend surface 51 of an adjacent link 50 c when articulation joint 50 is inthe straight configuration. When a second link 50 b is bent toward firstside 58 a, end surface 51 of the second link 50 b contacts end surface51 of an adjacent second link 50 b. When a third link 50 c is benttoward first or second sides 58 a, 58 b, end surface 51 of the thirdlink 50 c contacts end surface 51 of an adjacent third link 50 c.Contact between end surfaces 51 of adjacent links prevents furtherbending of adjacent links of articulation joint 50, and results in themaximum bend of articulation joint 50 in that specific direction.

Further, as shown in FIGS. 4A-4F, springs 24 are attached to all foursides 58 a, 58 b, 58 c, 58 d of second link section 54 and third linksection 56. The springs 24 are attached to adjacent links at offsetpositions, however. For example, three adjacent links 100 (see FIG. 3 )include two pairs of adjacent links. The first pair of adjacent links100A, 100B is attached together by springs 24 on first and second sides58 a, 58 b, such that the first pair of adjacent links 100A, 100B areunable to be bent relative to each other toward first and second sides58 a, 58 b. The second pair of adjacent links 100B, 100C is attachedtogether via springs 24 on third and fourth sides 58 c, 58 d. Secondpair of adjacent links 100B, 100C are therefore unable to bend towardthird and fourth sides 58 c, 58 d with respect to each other due to thearrangement of springs 24.

Adjacent links in each of first, second, and third link sections 52, 54,56 are capable of bending with respect to each other in at least onedirection. The angle at which adjacent links may bend and the spacingbetween these adjacent links may be equal to a smallest bend radius atwhich imaging wires and other components are capable of bending andremaining functional. For example, a largest bend angle B of adjacentlinks spaced apart by 0.3 inches to 0.7 inches is approximately 20degrees to 40 degrees, preferably approximately 25 degrees to 35 degreesat a 0.4 inch to 0.6 inch spacing between adjacent links, and morepreferably approximately 30 degrees at a 0.5 inch spacing betweenadjacent links.

Referring to FIGS. 4A-4C, longitudinal axis A extends in the Y-axis, andarticulation joint 50 bends in the Y-Z plane. As shown in FIG. 4B, afirst gap G is provided between adjacent links within the first linksection 52, and between a distalmost link in first link section 52 and aproximalmost link of second link section 54, along a first side 58 a ofarticulation joint 50. A second gap H is provided between adjacent linksin second link section 54 on first side 58 a. A third gap I is providedbetween links in third link section 56, and between a distalmost link ofthird link section 56 and distalmost link 29, on both first side 58 aand second side 58 b.

The first, second, and third gaps G, H, I allow articulation joint 50 tobend an amount equal to bend angle B multiplied by the number of totalgaps. For example, if bend angle B is 30 degrees and there are seventotal gaps on first side 58 a, articulation joint 50 may bend 210degrees from longitudinal axis A and allow tip 30 to point toward anentry point of endoscope 10 into the patient. The size of gaps G, H, andI may be varied to achieve a desired bend angle. It will also beunderstood that the bend angles are merely examples, and the bend angleof each different gap may be different for a gap type, e.g., eachdifferent gap G from the plurality of gaps G may have a different bendangle.

According to an example, third gaps I on second side 58 b allow adjacentlinks to bend at a same angle B as first gaps G. However, that angleassociated with third gaps I on second side 58 b is not limited to angleB and may be any angle that optimizes the bend angle of articulationjoint 50. As shown in FIG. 4C, third gaps I allow third link section 56and distalmost link 29 to bend away from longitudinal axis A towardsecond side 58 b while first link section 52 and second link section 54do not bend toward second side 58 b, i.e., first link section 52 andsecond link section 54 remain coaxial with longitudinal axis A. Thisconfiguration allows articulation joint 50 to bend 90 degrees towardsecond side 58 b. Since this bend is performed by bending at only somegaps, i.e., using only the three third gaps I, a bend radius ofarticulation joint 50 is reduced, thereby allowing articulation joint 50to bend in smaller spaces. It will be understood that while second linksection 54 is shown as being capable of bending in three directions,second link section 54 may be capable of bending in only two directionsin some examples.

Referring to FIGS. 4D-4F, longitudinal axis A extends in the Y-axis andarticulation joint 50 bends in the X-Y plane. As shown in FIG. 4E,second link section 54 and third link section 56 include a plurality offourth gaps J on a third side 58 c and a fourth side 58 d ofarticulation joint 50, opposite third side 58 c. Fourth gap J is alsobetween the distalmost link of second link section 54 and the proximalmost link of third link section 56, and the distalmost link of thirdlink section 56 and distalmost link 29. Fourth gaps J are not present infirst link section 52. According to an example, fourth gaps J permitadjacent links to bend at a same angle B as the angles associated withfirst, second, and third gaps G, H, I. However, the angle associatedwith fourth gaps J is not limited to angle B and may be any angle thatoptimizes the bend angle of articulation joint 50. As further shown bycomparing FIG. 4B to FIG. 4E, fourth gaps J are offset, or alternate,along longitudinal axis A from first, second, and third gaps G, H, I.For example, as discussed above, adjacent links may bend with respect toeach other in first and/or second directions 58 a, 58 b, but not inthird and fourth directions 58 c, 58 d, based on the arrangement ofsprings 24. Similarly, adjacent links may bend with respect to eachother in third and/or fourth directions 58 c, 58 d, but not in first andsecond directions 58 a, 58 b. Thus, in some examples, when a portion ofarticulation joint 50 is bent, two adjacent links may be bent together(e.g., first pair of adjacent links 100A, 100B may bend relative to eachother toward one side or another).

Articulation joint 50 may bend in the X-Y plane with respect tolongitudinal axis A. For example, if bend angle B is 30 degrees andthere are four gaps J on each of third side 58 c and fourth side 58 d,articulation joint 50 may bend 120 degrees with respect to first linksection 52 in both a left and right direction, i.e., toward third side58 c and fourth side 58 d (i.e., a 120 degree deviation of second andthird link sections 54, 56 from longitudinal axis A). This configurationagain limits the number of gaps necessary to achieve a desired bendangle of articulation joint 50, thereby reducing the bend radius ofarticulation joint 50 to allow for greater maneuverability in smallerspaces. It will be understood that as articulation joint 50 bends towardone or more sides, surfaces defining the gaps at those side approachuntil the surfaces are in contact with each other and the respectivegaps therefore completely close. A size of gaps on an opposite side ofthe bend will increase. Similarly, when articulation joint 50 moves froma bent position back toward the straight configuration, the closed gapsreopen, and the size of gaps on the opposite side of the bend willdecrease. It will be understood that the angle of gap J on third side 58c and the angle of gap J on fourth side 58 d do not need to be equal toeach other and/or do not need to achieve the same total deviation ofarticulation joint 50 from longitudinal axis A. For example, gaps may bearranged on third side 58 c and fourth side 58 d such that a number ofgaps and/or an angle of bend of the gaps on third side 58 c is differentthan a number of gaps and/or an angle of bend of the gaps on fourth side58 d, resulting in different bend geometry at full flexion ofarticulation joint 50.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed device withoutdeparting from the scope of the disclosure. For examples, theconfiguration of gaps and links and the bend angles may be altered tosuit any medical device. It will be understood that the bend angles,sizes of each gap, and/or the number of gaps and links are not limitedto the examples described herein. Other embodiments of the disclosurewill be apparent to those skilled in the art from consideration of thespecification and practice of the invention disclosed herein. It isintended that the specification and examples be considered as exemplaryonly, with a true scope and spirit of the invention being indicated bythe following claims.

What is claimed is:
 1. An articulation joint for a medical device, thearticulation joint including: proximal links, distal links, andintermediate links connecting the proximal and distal links, wherein thearticulation joint has a straight configuration along a straightlongitudinal axis, a first bent configuration when the articulationjoint bends toward a first side of the longitudinal axis, and a secondbent configuration when the articulation joint bends toward a secondside of the longitudinal axis, opposite to the first side, wherein, whenthe articulation joint is in the straight configuration: a first gap isdefined at the first side between adjacent proximal links, and theadjacent proximal links contact each other at the second side, a secondgap is defined at each of the first side and the second side betweenadjacent distal links, and a third gap is defined at the first sidebetween adjacent intermediate links, and adjacent intermediate linkscontact each other at the second side.
 2. The articulation jointaccording to claim 1, wherein when the articulation joint is in thefirst bent configuration, a size of each of the first, second, and thirdgaps on the first side, is smaller than a size of the first, second, andthird gaps on the first side respectively when the articulation joint isin the straight configuration.
 3. The articulation joint according toclaim 1, wherein when the articulation joint is completely bent towardthe first side, surfaces of adjacent links contact each other such thata size of each of the first, second, and third gaps on the first side iszero.
 4. The articulation joint according to claim 1, wherein when thearticulation joint is in the second bent configuration, a size of thesecond gaps on the second side is smaller than a size of the second gapson the second side when the articulation joint is in the straightconfiguration.
 5. The articulation joint according to claim 4, whereinthe distal links are movable in exactly four directions, the proximallinks are movable in exactly one direction, and the intermediate linksare movable in two or three directions.
 6. The articulation jointaccording to claim 1, wherein the articulation joint further includes athird bent configuration toward a third side of the longitudinal axis,intermediate to the first and second sides, and a fourth bentconfiguration when the articulation joint bends toward a fourth side ofthe longitudinal axis, opposite to the third side, wherein when thearticulation joint is in the straight configuration: a fourth gap isdefined at each of the third side and the fourth side between theadjacent distal links; and a fifth gap is defined at each of the thirdside and the fourth side between the adjacent intermediate links.
 7. Thearticulation joint according to claim 6, wherein when the articulationjoint is in the third bent configuration, a size of each of the fourthgaps and the fifth gaps on the third side is smaller than a size of thefourth gaps and the fifth gaps on the third side respectively when thearticulation joint is in the straight configuration, and wherein whenthe articulation joint is in the fourth bent configuration, a size ofeach of the fourth gaps and the fifth gaps on the fourth side is smallerthan a size of the fourth gaps and the fifth gaps on the fourth siderespectively when the articulation joint is in the straightconfiguration.
 8. The articulation joint according to claim 6, whereinthe fourth gaps and the fifth gaps are offset from the first, second,and third gaps along the longitudinal axis.
 9. The articulation jointaccording to claim 6, wherein the articulation joint is configured tobend toward one of the first or the second side and one of the third orthe fourth side at a same time.
 10. The articulation joint according toclaim 6, wherein a bend angle associated with each of the first, second,third, fourth, and fifth gaps is equal.
 11. The articulation jointaccording to claim 1, wherein the proximal links, distal links, andintermediate links of the articulation joint are each attached to anadjacent link by a first spring and a second spring, and wherein thefirst spring and the second spring of attached links are oncircumferentially opposite sides of the articulation joint.
 12. Thearticulation joint according to claim 11, wherein the first and thesecond springs are attached on an inner surface of each of the proximallinks, distal links, and intermediate links by one or more of laserwelding or an adhesive.
 13. The articulation joint according to claim11, wherein adjacent coils of each of the first spring and the secondspring contact each other when the first springs and the second springsare in a straight configuration.
 14. The articulation joint according toclaim 11, wherein each of the first spring and the second spring definesa lumen for containing an articulation element.
 15. An articulationjoint for an endoscope, the articulation joint comprising: proximallinks, distal links, and intermediate links connecting the proximal anddistal links, wherein the articulation joint has a straightconfiguration along a straight longitudinal axis, wherein the proximallinks are movable toward only a first side of the articulation jointaway from the longitudinal axis, wherein the distal links are movabletoward the first side, a second side, a third side, and a fourth side ofthe articulation joint away from the longitudinal axis, wherein thefirst, second, third, and fourth sides are equally spaced about thelongitudinal axis, and wherein the intermediate links are movable onlytoward the first side, the second side, and the third side of thearticulation joint away from the longitudinal axis.
 16. The articulationjoint according to claim 15, further comprising, in the straightconfiguration, gaps between links of the proximal links, the distallinks, and the intermediate links at locations where the articulationjoint bends, wherein when the articulation joint completely bends towardeach of the first, second, third, and fourth sides, surfaces of adjacentlinks contact each other along the respective side, and a size of thegaps along the respective side is zero.
 17. An endoscope, comprising: ahandle; and a catheter connected to the handle and extending distally,the catheter comprising: a shaft extending distally from the handle; atip member provided at a distalmost end of the catheter; and anarticulation joint connecting the tip member to the shaft, wherein thearticulation joint includes a proximal portion, a distal portion, and anintermediate portion arranged about a longitudinal axis, the proximalportion is bendable in only a first direction away from the longitudinalaxis, the intermediate portion is bendable in the first direction, asecond direction, a third direction, and a fourth direction away fromthe longitudinal axis, and the distal portion is bendable in only thefirst, second, and third directions.
 18. The endoscope according toclaim 17, wherein the distal portion, the intermediate portion, and theproximal portion of the articulation joint include a plurality ofadjacent links each connected by two springs on radially opposite sidesof the articulation joint.
 19. The articulation joint according to claim1, wherein: when the articulation joint is in the first bentconfiguration, the articulation joint bends, at a first bend radius, toa first bend angle that is a maximum bend angle, when the articulationjoint is in the second bent configuration, the articulation joint bends,at a second bend radius, to a second bend angle that is smaller than thefirst bend angle, and the first bend radius is the same as the secondbend radius.
 20. The articulation joint according to claim 11, wherein:the first and second springs attaching a first pair of adjacent links,including a first link and a second link, are respectively on a firstside of the articulation joint and a second side of the articulationopposite the first side, and the first and second springs attaching asecond pair of adjacent links, including the second link and a thirdlink, are respectively on a third side of the articulation joint,intermediate to the first and second sides, and a fourth side oppositethe third side of the articulation joint.